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<article class="example example-like"><h3 class="heading">
<span class="type">Example</span><span class="space"> </span><span class="codenumber">1.1.1</span><span class="period">.</span>
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\begin{align*}
{(a)}\amp  \quad \frac{dy}{dx}=x,\\ \\
{(b)}\amp  \quad \frac{\partial^2u}{\partial x^2}+\frac{\partial^2 u}{\partial y^2}=0.
\end{align*}
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